I'm not really sure who they answer to. It is no secret that back when these guys were being recruited to crush rivals and opposition, they were provided political cover and protection in return for their services. Since then, they've gained influence and now control a large portion of the direction of it's policies.
I would say they have an understanding with London, but to say that they answer to anyone other than themselves is untrue IMO. They have enough fire-power and influence to survive without London. It is actually London which falls without them.
Those hired guns are common thugs and criminals they can't exist without an ideological force. If it was only them then it would strictly become a police issue.